In a motor vehicle transmission, rotatable transmission input and output members are selectively coupled using interconnected gear elements and clutches to establish a range of transmission output speed ratios. Some clutches are usually embodied as fluid-actuated friction clutches having spaced clutch plates coated with friction material. A hydraulic piston may be used to compress the plates and thereby transfer torque across the engaged friction clutch, or to connect a rotating member to a stationary member in the manner of a brake. Friction clutches are typically controlled with a variable rate of slip such that the clutch state can range anywhere between fully-applied and fully-released.
In some transmissions, a binary clutch assembly is used in lieu of a friction clutch. A typical binary clutch assembly includes a freewheeling element and an on/off binary device such as a selectable one-way clutch or a dog clutch. Unlike conventional friction clutches, a binary device has just two possible clutch states, i.e., fully-applied and fully-released. When the binary device is unloaded upon a commanded release, the binary clutch assembly freewheels in at least one rotational direction. Application of the binary device, typically via deployment of spring-loaded struts, sprags, or other torque-holding pieces into engagement with recesses in a race of the binary device, thus effectively locks the binary clutch assembly to thereby present undesired rotation.